A discharge device (dispenser) for discharging a liquid material with the aid of a reciprocating plunger is known as a device to distribute the liquid material in steps of manufacturing electronic parts, etc. The discharge device is used, for example, to perform a desired application of the liquid material on a workpiece while the workpiece is horizontally moved relative to a worktable.
In one example of a related-art discharge device of the type causing the liquid material to land on the workpiece after having departed from a nozzle, a plunger rod is disposed within a flow path including a valve seat near an outlet that is communicated with the nozzle while a lateral surface of the plunger rod is held in a noncontact state, and a tip of the plunger rod is moved toward the valve seat to be impinged against the valve seat, whereupon the liquid material is discharged from the nozzle in a droplet state (Patent Document 1).
As to techniques of discharging the liquid material to fly in the form of droplets by abruptly stopping a plunger, which is moved forward at a fast speed, without impinging the plunger against a valve seat, the applicant has proposed a method and a device for discharging the liquid material in which a liquid-material discharging plunger having a tip surface held in close contact with the liquid material is moved forward at a fast speed, and a plunger driving means is then abruptly stopped to apply an inertial force to the liquid material, thereby discharging the liquid material (Patent Documents 2 and 3).
Furthermore, there is proposed a jetting dispenser including a jetting nozzle provided with a plurality of nozzle outlets in communication with a fluid channel outlet, and a valve member movably disposed within a fluid channel to be able to selectively contact a valve seat, wherein when the valve member comes into contact with the valve seat, a momentum sufficient to quickly jet a plurality of droplets from the plurality of nozzle outlets at the same time is given to the liquid material in the fluid channel outlet (Patent Document 4).